Major Incidents

I-25 Walnut Street Bridge Collapse

Walnut Street Viaduct over I-25 in Denver , under construction, collapsed during the early morning hours of Oct. 4, 1985, killing one construction worker and injuring four others. The new viaduct was being built to replace the old Larimer Street Viaduct.

Torpedoes in the Mousetrap

The Mousetrap, so dubbed by a radio reporter in the 1960s, is the intersection of I-25 and I-70 northwest of downtown Denver . It was so called because it supposedly looked like a mousetrap from the air, and because it was infamous for trapping vehicles within its network of sharply curving ramps.

In the early-morning hours of August 1, 1984, a truck carrying a load of torpedoes on I-25 exited onto one of the off-ramps and, apparently traveling and too high a speed, dumped the load under the various Mousetrap structures. The freeway was closed for miles in all directions for several hours. The result of this mishap was worldwide publicity, and the realization that the Mousetrap was inadequate to handle the estimated 300,000 vehicles daily.

In 1964, the portion of newly-designated (1957) I-70 from Colorado Boulevard west to I-25 was opened on an elevated structure above 46 th Ave. A modified interchange at I-25 was built (this interchange had previously served 46 th Ave. ). One year later, in 1965, the portion of I-70 going west from I-25 was opened. This portion was aligned with 48 th Ave.

Following the “Torpedoes in the Mousetrap” incident in 1984, plans were made to reconstruct the Mousetrap and the portion of I-25 that was first to open in Denver in 1951. See Mousetrap/I-70 North program notes below). In 1987, the 44 th Ave. , bridge over I-25 was replaced and I-25 beneath was widened to accommodate future HOV lanes. In 1989, construction of the new I-70 bridges over I-25 began. These bridges were completed and the ribbon cutting was held Dec. 27, 1991.

Improvements on I-25 in the area from 20 th Avenue north to 70 th Avenue continued largely unabated from 1987 until 1995. The freeway was widened, accesses were improved, and two high occupancy vehicle (HOV) lanes were built in the center of the freeway between 20 th Avenue near downtown to the 70 th Avenue bridge. While other highway improvements opened as they were completed, the HOV lanes were open to southbound vehicles with two or more passengers in the morning hours, and northbound in the afternoon rush hours. The lanes were also used to help heavy traffic rushes out of central Denver after large special events are held, such as Bronco football games at Invesco Field at Mile High.

1995 – CDOT announced that for the first time in six years, there will be no traffic delays on I-25 in Denver due to construction. The completion of the HOV lanes from downtown north to 58 th means there will be no major construction projects on I-25 in the metro area during the 1995 summer season.